Remove unnecessary methods and collapse function calls in the preloader code

Remove unnecessary methods and collapse function calls in the preloader code

- Remove PreloadRequest::defer()
- Remove ResourceFetcher::requestPreload(). The only user is preload()
  and is just calling requestPreload().
- Move setDefer() call in HTMLResourcePreloader::preload() into
  resourceRequest() call
- Make HTMLResourcePreloader::preload() private

R=japhet
BUG=none

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185100

[tyoshino (SeeGerritForStatus), 2014-11-10 05:51:22]

tyoshino@chromium.org changed reviewers:
+ japhet@chromium.org

[Nate Chapin, 2014-11-10 21:40:03]

Yay cleanup! LGTM

[tyoshino (SeeGerritForStatus), 2014-11-11 03:41:47]

The CQ bit was checked by tyoshino@chromium.org

[commit-bot: I haz the power, 2014-11-11 03:42:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/717453002/40001

[commit-bot: I haz the power, 2014-11-11 04:45:07]

Committed patchset #3 (id:40001) as 185100